Camaroking1996

Can you use 6 inch long connecting rods with the stock crank?

93M6Formula

Yes but have to have the right pistons that allow for the longer rod.
Someone else can elaborate on this, but the answer is yes.

Camaroking1996

Do as long as the pistons are suitable for the extra length it will work

quik95lt1

iTrader: (7)

pretty much what he just said yes you can use 6" rods with the stock crank but you will have to have a different compression height on th episton to make up for the .3" difference of the rod........pretty simple stuff

Camaroking1996

Also for a 355 build what compression and stroke would be good for a DD?

quik95lt1

iTrader: (7)

what u mean what stroke??? with a stock crank your stroke is 3.48" done end of story unless u replace the crank......also compression keep it under 11.25:1 for a 93 octane friendly car...........

i suggest you do some research before diving in too fast....

Camaroking1996

What about 10.3.1

quik95lt1

iTrader: (7)

also compression keep it under 11.25:1 for a 93 octane friendly car...........

Camaroking1996

Ok thanks

gregrob

iTrader: (8)

12:1 is fine on 93, especially with a healthy cam.

You need pistons with a 1.250 Compression Distance for that rod stroke combo

Most aftermarket pistons are designed for use with a 3.50 inch crank with a 9" compression distance. Using them with a stock crank puts the piston at 8.990 which is totally fine. One just needs to keep this on mind to specify squish clearance, deck height, hg thickness, target compression, PTV clearance, etc.

quik95lt1

iTrader: (7)

true on the compression but im just being safe for him...........lol

Camaroking1996

Thanks fellas and one more thing is there any advantage to using 6 inch rods instead of 5.700?

quik95lt1

iTrader: (7)

IMO......nope

duh

iTrader: (16)

I was just doing some research on this actually. According to the guys at Reher-Morrison, on an engine that lives under 9000 RPM there is NO gain. Above that there is something to be said about having a longer rod and it's inherent ability to keep the skirts happy due to less piston rock in the bore, but for a daily driver or a race engine that doesn't go over 9K rpm you won't see any gain. Infact they stress using whatever rod necessary to use your desired compression height and stroke. And these guys build 2500HP motors on a daily basis, so I'd trust them.

quik95lt1

iTrader: (7)

you are correct.......on a shorter stroke motor like with the stock crank there is no advantage once so ever unless you are running major and i mean major rpm........it will actually reduce ur durability because of the height of the piston pin in the skirt putting it in the oil ring..........

heres a pic of the piston out of my 385 with a 6" rod........see how the pin is interfering with the oil ring.......creating the need for a support rail


on a 383+ it is worth the 6" rod for the exact reason stated above.....it makes the angle of the rod less, putting less wear on the cylinder walls and creating less heat and parasitic loss........

just run the 5.7 rod its ur best and easiest bet and there are more pistons avialiable as well off the shelf

duh

iTrader: (16)

yeah I've been doin some research about going 408 and spraying the crap out of it, but the idea is keep it under 7K to keep some sort of durability. The only problem is with durability comes price. Out of curiosity, what was the compression height on those pistons?

Sorry for the hijack

Camaroking1996

So basically for a DD just use the stock 5.7 rods

duh

iTrader: (16)

you can use stock as they have been proven to very good HP levels, or you can upgrade to an h-beam or a nice forged I-beam. Either way your cheapest route would be to reuse the stock if you can. Maybe have them install ARP rod bolts, and resize the big end accordingly, but that will add to the cost. It truly depends on your HP goals.

Camaroking1996

I'm going the route of SRP flat top pistons and compstar h beams

quik95lt1

iTrader: (7)

1.125"........personally i think 408 is too much stroke for these blocks which is why i built a 3.75" stroke motor......of course i planned on taking it above 8000rpm so ur case is a bit different.....

great choice!!!!!!